Abstract: Method and apparatus for monitoring wavelength shift in a holographic light protection filter to determine if the hologram has been damaged by moisture. The hologram is provided with first, second and third areas. The first area is an extra moisture protected area covered by a moisture resistant material. The second area is adjacent to the first area and is recorded at a different wavelength than the bulk of the hologram. The third area is the remainder of the hologram. The user compares light reflections at these specific areas of the hologram and observes color variations to determine if the hologram has been damaged by moisture. In another embodiment, scribe lines are drawn in the hologram through the three areas. The user detects moisture damage by observing the apparent displacement of these scribe lines in the three areas when viewed through a diffraction grating.

Abstract: A method and apparatus for forming a multiple exposure hologram includes an object beam cut out mask 24 and reference beam cut out mask 60. Different segments of the masks are left uncovered during each exposure step and operate to shape the reference 18 and object 16 beams so that they illuminate selected areas of the photosensitive plate 12. The angle of incidence of the object beam 16 remains constant during each exposure step while the reference beam 18 illuminates the plate 12 at different angles during each exposure step. During playback, a plurality of lamps 94-106 project reconstruction beams at the hologram 12 to individually or collectively render the holographic segments viewable with a minimum of crosstalk between each segment. In the preferred embodiment, the reference beam mask includes diamond-shaped cut outs 62-74 which are selectively used with associated object beam mask cut outs 28-40 to generate a hologram in the form of a seven-segment display.

Abstract: A method and apparatus for forming a multiple exposure hologram includes an object beam cut out mask 24 and reference beam cut out mask 60. Different segments of the masks are left uncovered during each exposure step and operate to shape the reference 18 and object 16 beams so that they illuminate selected areas of the photosensitive plate 12. The angle of incidence of the object beam 16 remains constant during each exposure step while the reference beam 18 illuminates the plate 12 at different angles during each exposure step. During playback, a plurality of lamps 94-106 project reconstruction beams at the hologram 12 to individually or collectively render the holographic segments viewable with a minimum of crosstalk between each segment.